The present invention relates to a silicon thin film transistor utilized in an active matrix type liquid crystal display device and a method for producing the same.
Referring initially to FIG. 26, there is shown an example of a conventional silicon thin film transistor which includes an insulating substrate 21, a gate electrode 22 thereon, a gate insulating layer 23 on substrate 21 and electrode 22, an impurity contained silicon layer 24 containing a suitable amount of impurities which become a donor or an acceptor, an intrinsic silicon layer 25 disposed between gate insulating layer 23 and silicon layer 24 and which becomes an active layer, a protective insulating layer 26, a source electrode 27 and a drain electrode 28.
As shown in the same Figure, such a silicon thin film transistor in which intrinsic silicon layer 25 and protective insulating layer 26 have been continuously formed, has excellent reliability, reproducibility of characteristics, and the like, and research and development thereof is widely carried out thereon.
In the above-described conventional silicon thin film transistor, protective insulating layer 26 formed by use of silicon nitride, silicon oxide, or the like is removed to expose intrinsic silicon layer 25, and an impurity contained silicon layer 24 is formed on this exposed intrinsic silicon layer 25.
However, at the protective insulating layer side of intrinsic silicon layer 25, there is a layer in which nitrogen, oxygen, or the like contained in protective insulating layer 26 has diffused. When protective insulating layer 26 is removed, this layer in which nitrogen, oxygen, or the like has been diffused is not completely removed. Accordingly, the junction of the intrinsic silicon layer and the impurity contained silicon layer becomes insufficient, resulting in deterioration of the transistor characteristics.
The present invention solves the above-described problems by improving the junction state of the intrinsic silicon layer and the impurity contained silicon layer to provide a silicon thin film transistor having good transistor characteristics, and a method for producing the same.